Fan.



J. F. HANRAHAN.

FAN.

APPLICATION FILED OUT- 6, 1909. I 997,8Q8 Patented July 11, 1911.

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FAN.

Specification of Letters Patent.

Application filed October 6, 1908.

Patented July 11, 1911.

Serial No. 521,321.

T 0 all whom it may concern:

Be it known that I, J osnrH F. ITANRAHAN, a citizen ofCanada, and resident of Buffalo, in the county of Erie and State of New York, have invented a new and useful Improvement in Fans, of which the following is a specification.

This invention relates to a fan which is more particularly designed for use in circulating air through a drier or evaporator but which may also be used for other pur poses.

The object of this invention is to produce a fan for this purpose whereby a large volume of air is positively and uniformly propelled through a conduit or passage of considerable length in the direction of the axis of the fan, as for instance, the air supply passage of a drying chamber which is equal in length to the entire length of said chamber.

In the accompanying drawings consisting of 2 sheets: Figure 1 is a Vertical cross section of an evaporator showing one application of my improved fan. Fig. 2 is a fragmentary horizontal section thereof, on an enlarged scale, in line 2-2, Fig. 1. Fig. 3 is a horizontal section, on a reduced scale, in line 3-3, Fig. 1. Fig. 4; is a vertical longitudinal section in line 11, Fig. 1.

Similar letters of reference indicate corresponding parts through the several views.

A represents the drying chamber of a kiln which receives the products or articles to be dried and which may be of any suitable form or construction. One of the longitudinal walls of this chamber is provided adjacent to the bottom of the chamber with an air inlet a and adjacent to the top thereof with an air outlet a said inlet and outlet of the chamber extending horizontally the full length of the chamber or substantially so, as shown in Figs. 3 and 4:.

B represents the case of a fan which is preferably arranged outside of the wall of the drying chamber containing the air inlet and outlet and extending the full length of the chamber, or substantially so, and parallel therewith. On the upper outer part of the periphery of the fan case the same is provided with a tangential air inlet 6 which is connected by an upper inclined air conduit or pipe O with the upper air outlet of the drying chamber. On the lower inner part of the periphery of the fan case the same is provided with a tangential air outlet b whicn is connected by a lower horizontal air conduit or pipe D with the lower air inlet of the drying chamber. The upper and lower conduits O, D are co-extcnsive with the fan case and drying chamber, as shown in Figs. 3 and 4:.

lVithin the fan case are arranged a plurality of longitudinal fan blades E which rotatevertically and are mounted by means of arms E on a horizontal shaft 6 arranged lengthwise in the fan case and driven in any suitable manner.

That side f of the periphery of the fan case between the inner angles of the tangential inlet and outlet is arranged. concentrically with the axes of the fan blades and case and the opposite side 7 of the periph cry of the case between the outer angles of the tangential inlet and outlet of the fan case is of scroll form or arranged eccentrically to the axes of the fan case and blades being of gradually increasing radii from the tangential inlet to the tangential outlet of the fan case. as shown in Fig. 1. The direction of rotation of the fan blades is such that when passing the eccentric side of the pe riphery of the fan case they move from the shorter to the longer radii thereof. By this means the air carried around by the fan blades within the concentric part of the periphery of the case is confined against outward radial movement under the centrifugal action of the fan blades but when the latter pass the eccentric part of the periphery of the case the air at this time is permitted to move radially outward a limited extent and produce a downward suction of the air from the upper part of the drying chamber through the upper air conduit and into the fan case from which latter it is again forcibly expelled through the lower air pipe into the lower part of the drying chamber wherein it again rises to the top, being forcibly and continuously circulated in this manner so long as the fan is in operation.

In the absence of any provision to prevent it, the rarefication of the air at the axis of the rotary fans due to the centrifugal action of the latter would cause a conflict of air currents at this place which would interfere with the propelling eifect of the fan blades on the air for withdrawing the same from the top of the drying chamber and returning the same to the bottom thereof, this being particularly the case in comparatively long fans. To avoid this, means are provided whereby suflicient air is diverted from the air inlet of the fan case to the axis of the blades to compensate for the air which is withdrawn from this location by the cen trifugal action of the fan blades. The preferred means for accomplishing this result consists in dividing the fan blades into plurality of groups, or sections each group containing a circumferential row of blades and the several groups being arranged lengthwise side by side on the fan shaft, as shown in Fig. 4, and providing auxiliary air supply conduits g which are arranged adjacent to the ends of the groups of the fan blades and each of which extends from the air inlet of the fan case to the axis of the blades. These auxiliary air conduits are formed by vertical partitions or dia phragms arranged in the fan case between the ends of adjacent groups of blades and between the ends of the fan case and the adjacent ends of the fan sections and extend ing from the inlet to the outlet thereof and having air inlet eyes in line with the axis of the blades. As the fan blades rotate that part of the air which is forced outwardly from the center of the same by the centrifugal action of the blades is replenished by the air supplied through the auxiliary air conduits 9, thereby preventing any back pressure or clashing of the air currents and enabling a large volume of air to be propelled by the fan with the expenditure of comparatively little power.

H has been found in practice that owing to slight differences in construction in different parts of the fan case, its inlet and outlet, the blades of the fan and the means for driving the same, which differences are practically impossible to avoid, air is propelled less effectively and at a slower speed or pressure upon issuing from some parts of the outlet than at other parts of the outlet, this being particularly noticeable at points between the ends of a fan section. T 0 overcom this variation in air pressure of the fan along its outlet, one or more equalizing air tudes are provided, whereby a part of the air admitted to the fan case at one or more of its eyes is conducted inwardly and lengthwise of its axis to the place where a test of the fan has demonstrated that a deficient air pressure exists. When the air pressure is deficient at several points or regions of the fan outlet, a plurality of equalizing air tubes are employed each extending from the eye of the fan case to the particular region where the air supply should be augmented.

as shown in the drawings, three of such equalizing air tubes H, H H of different lengths and diameters are arranged at opposite ends of each section of the fan. The equalizing tubes of each group are supported concentrically on the adjacent arms of the fan blades and have their outer ends arranged adjacent to the respective eye of the fan case while their inner ends terminate at different points inwardly from the end of the fan case, the innermost equalizing tube ll being longest while the intermediate and outer tubes H T1 are successively shorter. The diameter of the outermost equalizing tube is preferably less than the diameter of the adjacent eye of the fan case, so that the air supplied by the auxiliary conduit 9 and passing through the eye is delivered partly to the adjacent ends of the fan blades while other parts pass inwardly through the equalizing tubes and are distributed at the inner ends of these tubes into different parts of the axis of the fan case.

i or the purpose of further aiding equalization of the air pressure of the fan, the equalizing tubes may be provided with open ings 7b which are formed therein as required and operate to conduct air to such parts of the axis of the fan case as may be found necessary to effect a balance or equalization of the air pressure throughout the entire ength of the outlet of the fan.

By means of this fan, a uniform draft of air into the upper air conduit and a uniform blast of air from the lower air conduit is produced throughout the entire length of these conduits which causes a current of air of uniform density and speed to rise from the lower to the upper part of the drying chamber and thereby operate alike on the products in all parts of this chamber, thereby avoiding the necessity of re-drying part of the products in a charge as has been customary heretofore with consequent loss of efliciency in the apparatus and loss of uniformity in the product.

The vapors which are taken up by the air in passing the products to be dried are condensed by intercepting the air by means of a condenser on its way to the fan which condenser preferably consists of water conducting coils K which are arranged in front of the upper air outlet of the chamber and from which the water of condensation drips upon a gutter or pan Z leading to a sewer or receptacle.

The air freed from vapors upon being returned to the lower part of the drying chamher is preferably heated so as to increase its vapor absorbing capacity. The means for this purpose may consist of heating coils or pipes in arranged in a horizontal row in the lower part of the drying chamber, as shown in Figs. 1 and 3. The coils m may be heated by circulating a suitable heating agent through the same such as steam or hot water.

It is of course understood that the propelling effect of the fan is aided by the natural tendency of the cool column of air in the upper and lower air conduit and fan case to descend by gravity and the hot or warm air in the drying chamber to rise. \Vhen, however, the article or product to be dried requires treatment under comparatively low temperatures, as is the case in drying of glue and similar material, the thermal action of the air, if solely depended on, would produce a comparatively slow circulation of the air which would prolong the period of drying in the same measure. By the use, however, of this fan, the movement of the air is accelerated and the drying operation expedited, thereby materially increasing the output of the evaporator and reducing the cost of operation.

I claim as my invention:

1. A fan comprising a circular case having an inlet at one part of its periphery and an outlet at another part of its periphery, an equalizing tube arranged at the axis of the case and terminating in straight ends, and blades rotatable within the case.

2. A fan comprising a circular case having an inlet at one part of its periphery and an outlet at another part of its periphery, an equalizing tube arranged at the axis of the case and terminating in straight ends and having perforations, and blades rotatable within the case.

3. A fan comprising a circular case having an inlet at one part of its periphery and an outlet at another part of 1ts periphery, blades rotatable within the case, an auxiliary air conduit extending from said inlet to the blades at the axis of rotation, and an equalizing tube arranged at the axis of the fan and terminating in straight ends.

4:. A fan comprising a. circular case having an inlet at one part of its periphery and an outlet at another part of its periphery, blades rotatable within the case, an auxiliary air conduit extending from said inlet to the blades at the axis of rotation and an equalizing tube arranged lengthwise of the axis of the fan and terminating in straight ends and turning with said blades and extending inwardly from said auxiliary air conduit.

5. A fan comprising a circular case having an inlet at one part of its periphery and an outlet at another part of its periphery, blades rotatable within the case, an auxiliary air conduit extending from said inlet to the blades at the axis of rotation, and a plurality of equalizing air tubes of different diameter and lengths arranged concentrically and lengthwise of the axis of the fan and terminating in straight ends and turning with said blades and extending from said auxiliary air inlet inwardly and terminating at different regions within the axis of the fan.

Witness my hand this 4th day of October, 1909.

JOSEPH F. HANRAHAN.

Witnesses:

THEO. L. PorP, ANNA Hmrers.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). C. 

